| 11 | namespace vfs { |
| 12 | |
| 13 | auto Seek(File* file, int64_t offset, SeekWhence whence) -> Expected<uint64_t> { |
| 14 | if (file == nullptr) { |
| 15 | return std::unexpected(Error(ErrorCode::kInvalidArgument)); |
| 16 | } |
| 17 | |
| 18 | LockGuard<SpinLock> guard(GetVfsState().vfs_lock_); |
| 19 | if (file->ops != nullptr) { |
| 20 | return file->ops->Seek(file, offset, whence); |
| 21 | } |
| 22 | |
| 23 | // 默认实现 |
| 24 | uint64_t new_offset = file->offset; |
| 25 | |
| 26 | switch (whence) { |
| 27 | case SeekWhence::kSet: |
| 28 | if (offset < 0) { |
| 29 | return std::unexpected(Error(ErrorCode::kInvalidArgument)); |
| 30 | } |
| 31 | new_offset = static_cast<uint64_t>(offset); |
| 32 | break; |
| 33 | case SeekWhence::kCur: |
| 34 | if (offset < 0 && static_cast<uint64_t>(-offset) > file->offset) { |
| 35 | return std::unexpected(Error(ErrorCode::kInvalidArgument)); |
| 36 | } |
| 37 | new_offset = |
| 38 | static_cast<uint64_t>(static_cast<int64_t>(file->offset) + offset); |
| 39 | break; |
| 40 | case SeekWhence::kEnd: |
| 41 | if (file->inode == nullptr) { |
| 42 | return std::unexpected(Error(ErrorCode::kFsCorrupted)); |
| 43 | } |
| 44 | if (offset < 0 && static_cast<uint64_t>(-offset) > file->inode->size) { |
| 45 | return std::unexpected(Error(ErrorCode::kInvalidArgument)); |
| 46 | } |
| 47 | new_offset = static_cast<uint64_t>( |
| 48 | static_cast<int64_t>(file->inode->size) + offset); |
| 49 | break; |
| 50 | default: |
| 51 | return std::unexpected(Error(ErrorCode::kInvalidArgument)); |
| 52 | } |
| 53 | |
| 54 | file->offset = new_offset; |
| 55 | return new_offset; |
| 56 | } |
| 57 | |
| 58 | } // namespace vfs |